Offbeat or slightly crazy or amusing,
When something goes wrong,
A greeting or goodbye reserved for someone of whom you are especially fond.

A fantastic concert would be described as "Totally Bonkercockie" or "What a Bonkercockie evening"
"It's all gone bonkercockie" would be used to describe a task which begins well but fails at the final hurdle.
Bonkercockie - A Humorous farewell.